Preparation of soluble oil



Fb 25 594 H. L. JOHNSON ETAL. 29595927 PREPARATION 0F SOLUBLE OIL FiledMay e, 194s Arrow/V- Patented Feb. 26, 1946 yUNITED STATES PATENTGFF-ICE 2,395,627 PREPARATION F SOLUBLE OIL Herbert L. Johnson,4Norwood, and John Harold Perrine, Prospect Park, Pa., assignors to SunOil Company, Philadelphia, Pa., a corporation of New J erse'yApplication May 6, 1943, Serial No. 485,844

9 Claims.

, This invention relates to soluble oils and to.

The so-called soluble oils, which .comprise homogeneous mixtures of oiland emulsifying agent, constitute a well recognized and distinctA typeof product. They are distinguished from oils such aS used for enginelubrication particu- Y larly in that they have capacity for dilutionwith Water to form oil-in-water emulsions whereas engine lubricants donot possess this characteristic. The soluble oils are used widely in thearts as cutting oils, spray oils, rust-proofing oils or the like. Insuch applications the oil is employed in aqueous dilution in the form ofan oil-in-'water emulsion. Probably the widest' application for solubleoils is as cutting oils in metal working operations, such as cutting,"grinding, boring, grooving, cold-drawing and the like, in which theoil-v Water dispersion serves the two-fold purpose of a lubricant and acoolant for the metal being fabricated. Among the essential requirementsof high-grade cutting oils may be mentioned thel ability of theundiluted oil to remain homogeneous under storage conditions, theability to form exmany useful applications in the arts, either asIfractions of relatively pure chemical type or as mixtures of varioustypes having characteristics desirable for specific purposes, providedthe proper segregation of components into fractions could be effected.However, due to the complexity of the oxidized material, not only hasresolution of the mixture into fractions of relatively will. result infailure of the process.

carbons. 'cially successful process no doubt has been due pure chemicaltype so far proved to be impossible, at least on a commercial scale, butalso the segregation of fractions having properties suitable for variousspecific uses heretofore has been exceedingly difficult to accomplishand in most cases impractical as a commercial operation.

It also is known to prepare soluble oils from certain naturallyoccurring petroleum acids,

commonly called naphthenic acids. U. S. Patent No. 2,056,913, issued toTerrell et al., describes a method of recovering such acids andpreparing soluble oils therefrom. However, as far as applicants areaware, no process of commercial value has been known heretofore forpreparing high-grade soluble oils from synthetic acids derived bypartial oxidation of petroleum hydro- Previous failure to provide acommertothe complexity of the oxidized mixture, i. e. the presence ofdiilicultly separable types of compounds having characteristicsdetrimental to soluble oils along with the desiredcomponents.

The present invention provides a commercially feasible process ofoxidizing petroleum hydrocarbons and separating from the oxidationproduct an acidic fraction in which detrimental constituents, aresubstantially absent and which therefore may be'used to prepare solubleoil of highest quality. The process comprises a series ofinterrelatedstepseach of which functions as a part ofa unitary procedure andcontributes to the success of the process as a whole.

More specifically, the present invention provides a method of producingsoluble oil, which includes the following procedural steps in the ordernamed:

With the exception of step 3, all steps are so' vital to the successfulproduction of high quality soluble oil that the elimination of any onestep Also substantial variations in operating conditions as set forthhereinafter likewise may cause failure. Although step 3 may be omittedwithout affecting the quality of the final product, its inclusion ishighly desirable for economic commercial operation, as hereinaftermorefully explained.

Fractional acidication of the deoiled sa- For a general understanding ofthe process to which this invention is directed, reference should be hadto the accompanying drawing which diagrammatically illustrates theprocedural steps. The process preferably is carried out in a batchwisemanner and will be described as such herein, although, as will beobvious ,to those skilled in the art, it may be conducted also as acontinuous process.

The first step in the process comprises subjecting a charge stock toliquid phase partial ox-. idation in the absence of a special catalyst.Preferably fresh charge stock, comprising a mineral oil meeting certainspecications as hereinafter set forth, is blended with unsaponifiablematerial'separated from a previous batch o f oxidized oil, hereinafterreferred to as recycle stock. and the blend is oxidized at a temperatureof 13o-150 C., preferably 140 C.. by blowing therethrough and intimatelycontacting therewith a free-oxygen containing gas, preferabLv air, undera superatmospheric pressure, preferably 50-100 pounds per square inchgauge. A stream of vent gases, containing the lowest boiling oxidationproducts, is withdrawn from the oxidation zone continuously throughoutthe oxidation period and` may be passed to a. condenser or othersuitable equip ment for recovery of the contained oxidation products.The oxidation preferably is continued until the batch has asaponiication value of 110-120 nig. KOH/gram, the corresponding acidnumber being about 50-55, at which point the maximum yield of desirablereaction products is reached. The resulting mixture, comprisingoxidation products of numerous chemical types and unoxidized oil, istreated with a strong aqueous solution of an alkali metal hydroxide,preferably. caustic soda, in the theoretical amount required forcomplete saponification. A Mixing is eiected at sufficiently hightemperature, preferably 80-90 C., and for sufficient length of time tosaponify all the esters and other diflicultly saponiiiable constituents,completeV saponication being very important for obtaining a productsuitable for producing high-grade soluble oils. After completesaponification thesoap-oil mixture is-diluted with a relatively largeproportion of water, preferably three volumes of water being added foreach volume of the oily mixture of products from the oxidation step, andthe resulting mixture is allowed to settle, preferably at a temperatureof SLP-90 C., until a clean separation of aqueous and oil phases isobtained. Soaps of relatively low molecular weight acids act here asde-emulsifying agents and play a major role in effecting a sharpseparation of the two phases. The oil phase, comprising unoxidized oiland unsaponiiiable water-insoluble oxidation products such as alcohols,aldehydes and ketones, separately is withdrawn `and returned as recyclestock to the oxidation step, where it is blended with fresh charge stockand further subjected to oxidation. lis later shown, this recycle stockhas a catalytic effect in the oxidation step and serves to promote thedesired oxidation reaction.

It is noted that the aqueous soap layer result- I material has beenfound to be not only beneficial but even necessary for compoundingsoluble oil of the highest quality from the product resulting from thesubsequent purification steps.

The next step in the process comprises subjecting the -aqueous soaplayer to partial or fractional acidication, preferably at a temperatureof 80-90 C. Prior to carrying out this operation, it is desirable,although not requisite, that a light lubricating oil of the type tobe,used in the nal step of compounding the soluble oil, for instance adistillate oil having a viscosity of 100 seconds S. U. at 100 F., beadded to facilitate separation of layers in both the present step andthe subsequent water washing step. The added oil promotes the separationmainly by lowering the specific gravity of the resulting synthetic acidlayer, which otherwise would have a gravity of approximately 0.98, ifpreferred starting material had been used, or in other words notconsiderably less than that of the aqueous phase. A suitable amount ofsuch oil to add is that equal in volume to the fresh charge stock whichhas been subjected to oxidation. After such addition, the mixture issubjected to fractional acidification by treating with a strong mineral.acid, preferably sulfuric acid, in amount suiiicient to acidify only afraction of the soaps. The correct proportion of mineral acid to usedepends somewhat on the particular conditions obtaining in the oxidationstep and the degree of oxidation effected, especially on the proportionof Oxy-acids formed. For the preferred conditions, the correctproportion is that equivalent to ,about per cent of the alkali employedin the saponication, or in other words an amount of mineral acidequivalent to only about 50 per cent of the carboxyl groups. It has beendiscovered that such partial or fractional acidication selectivelyconverts to acids the soaps of the weaker acids, i. e. of those havingthe lower dissociation constants, while leaving soaps of stronger acidsunaffected. It also has been discovered that these stronger acids,comprising the lower molecular weight acids and oxyacids, are highlydetrimental and therefore must be substantially absent from the puriedproduct s from which soluble oil of the present invention is compounded.After partial acidification, the mixture is allowed to settle,preferably at -90 C., until a clean separation is obtained. As in thepreceding deoiling step, soaps of the low molecular weight acids serveas de-emulsifying agents. The resulting lower layer, comprising anaqueous solution or dispersion of soaps of the stronger acids (lowmolecular weight acids and Oxy-acids) and, in addition, anyWater-soluble unsaponifiable products of the oxidation such as lowmolecular weight alcohols, aldehydes or ketones not removed in the ventgases from the oxidation step, is drawn off and either discarded orseparately processed for recovery of contained oxidation products.

The upper layer comprises a mixture of the weaker carboxylic acids andoil and, in addition, contains some soaps as well as some water-solublefree acids as contaminants. These soaps and water-soluble acids,although present in relatively small amounts, would be highlydetrimental if allowed to remain in the mixture and so must be removedbefore compounding of the soluble oil. This is accomplished by agitatingthe layer,

'preferably still at 80-90 C., with an equal'volume of water, allowingthe resulting mixture to stratify and withdrawing the aqueous layer withthe said contaminants dissolved therein. The removed aqueous layer maybe added to the soap layer obtained after the fractional acidificationstep and separately processed therewith or may be discarded. The washedoily layer may contain some water insuspension which may be removed byblowing with air.

'I'he refined synthetic acid product 'resulting from the above outlined4procedure is a particu larly suitable stock for compounding soluble cilof excellent quality according to the formula and procedure hereinafterdisclosed and described. It also may be used for preparing products ofvarious other types such as greases, metallic derivatives for colorlakes, siccatives or organic salt catalysts.

The starting material of the process outlined above consists of apetroleum fraction of lubricating oil consistency, containing asuiiicient proportion of naphthenic constituents so that an average ofat least one naphthene ring per molecule obtains. The `naphthenicconstituents are desirable in order that the acidic product obtained byoxidation and subsequent purification will resemble natural naphthenicacids rather than fatty acids, since naphthenic acids `havecharacteristics making them more suitable than fatty acids for theproduction of soluble oils of -the type herein concerned. Moreparticularly,

soluble oils prepared from naphthenic acids should be slightly alkalinefor-best results whereas those prepared from fatty acids should beacidic (i. e. containing free fatty acids). Since the desired product ofthe present invention is the alkaline type soluble oil, it accordinglyis desirable that the synthetically produced acidic material resemblesnatural naphthenic acids in this respect. The desirability of having-suflcient naphthenic components in the starting material does notnecessitate the use of petroleum fractions derived only from theso-called naphthenic base crudesjalthough these are preferable,lfor inmany cases fractions derived from either mixed base or paraiin basecrudes contain sufficient naphthenic components to be useful.

Another prerequisite .of the starting material is that it should notcontain more than a certain maximum concentration of aromaticcomponents. It has been found that aromatics greatly increase theresistance of the oil to oxidation, apparently having an inhibitingeffect on the oxidation of the other ltypes of components present. Whensuiiiciently severe oxidizing conditions are employed to' forceoxidation 'of highly aromatic oils, there is a tendency toward theformation of sludge rather than the desired oil-soluble acidic reactionproducts. The maximum concentration of aromatics, above which thedesired oxidation cannot be effected, depends on two factors. First, themaximum allowableconcentration is related to the molecular weight of thestarting material; the lower the molecular weight the Ygreater being theallowable concentration. Section rates:

Proportion of aromatic rings 270 S. U.` viscosity stock without recycle270` S. U. viscosity stock with recycle l Not over 7% Kerosene withrecycle Not over 16% Not over 4% The synthetic acids resulting from theoxidabase crudes, a viscosity range of 150-350 seconds S. U. at 100 F.corresponds to a molecular weight range suitable for the preparation ofsoluble oils according to the invention, although the preferredviscosity of the starting material isy about 270. Low molecular weightfractions, such as kerosene, give reaction products of too low molecularweight to` be suitable in the present applical tion.

Most petroleum fractions of suitable molecular weight range, .which havebeen obtained from crude petroleum by the usual distillation procedurewithout further treatment, contain too high an aromatic content to beuseful per se as charge stock for the process and therefore requirepretreatment to reduce the concentration of aromatics therein. Anysuitable pretreatment whereby the concentration of aromatics is reducedsufficiently may be used; for instance, solvent extraction or treatmentwith concentrated or fuming sulfuric acid may be employed. The lattermethod, which has been used widely in the arts for the production ofso-called white oils, is a convenient means of preparing suitable chargestock. For instance, a 270 viscosity oil Aromatic rings Naphthenic ringsParailinic chains Itis noted that for any given oil the refractive indexof the oil affords a convenient means of determining when the aromaticcontent is sufciently low, and is used in preference to the somewhat'diicultWatermann analysis method as a means of routine control of thepretreating step. Thus for an oil such as the above, a refractive indexbelow '1.4890 indicates that the oil may be oxidized withoutthe additionof recycle stock, an index of 1.4890-1.4920 lindicates that the oil willoxidize satisfactorily if mixed with recycle 5 stock, and an index above1.4920 indicates that the oil will not oxidize properly even ifrecycling is employed.

In the oxidation step the main factors affecting therate of oxidation,besides the aromatic content of the charge and the effect of recyclingas indicatedabove, are pressure and temperature. The air rate appears tohave little eifect provided the exit or vent gas contains a substantialpercentage of free oxygen. In order to ensure a practicaloxidation rate,the pressure should be maintained above atmospheric pressure. generallyabove 25 pounds per square inch gauge, but not in excess o! about 175,and preferably should be 50-100. At the preferred temperature a pressurebelow about 25 gives a rate of oxidation which is too slow to bepractical. As the pressure is increased, the reaction rate alsoincreases kuntil a pressure of about 100 pounds per square inch isreached; whereupon further increases cause the rate to diminish, untilat a pressure exceeding about 175 the rate again has become undesirablyslow. It has been discovered that this decrease in rate at pressuresabove about 100 pounds per square inch is due to retention of lowboiling oxidation products in the reaction mixture and that suchproducts retard or inhibit the oxidation reaction. At lower pressuresthese low boiling products. on forming, rapidly are removed in the ventgas and so do not affect the reaction rate appreciebly.v

The temperature at which the oxidation suitably may be carried out isconiined to a relatively narrow range. With a charge stock such as theone described above, a temperature of approximately 140 C. gives thebest results although any 'temperature within the range of about 130-150C. may be used. Below this range, for example at 120 C., the rate ofoxidation is exceedingly slow; on the other hand at temperatures aboveabout 150 C., say at about 155 C. and higher, there is formed4 anundesirable oilinsoluble sludgelike .product having no utility in thepresent application. The optimum temperature and the limits oftemperature for practical commercial operation may vary somewhat,depending on the composition and molecular weight of the charge stock,and therefore a definite optimum temperature or the limits oftemperature suitable for all charge stocks cannot be speciiied. In allcases, however, the temperature should be suiliciently high to give acommercially practical rate of oxidation but not so high as to cause theformation of sludge-like products. It appears that temperatures lowerthan about 120 C. or higher than approximately 165 C. are seldom if eversuitable.. n

It obviously is desirable that the oxidation be .carried to ,such adegree as to eiect maximum yield of the desired product, and it has beenfound that this maximum is obtained when the oxidized oil reaches asaponication value of about 110-120 at which point the correspondingacid value is about Sil-55. Itlis permissible to stop thereaction at anypoint short of this degree of oxidation provided the product obtainedfrom the subsequent purifying procedure has. a, saponiiication valuesuiliciently high to produce soluble oil according to the formulahereinafter disclosed; for

instance, the reaction might be stopped when the.

saponlfication value is even as low as about 30.

of pentane,'the following approximate percenty ages of pentane-insolubleproducts were obtained: y

Saponliicaton Percent value oi recutaneaction mixture, oluble mg. KOH/g.products Although these values for pentane-insoluble productsprobably-include small percentages of low molecular `weight acids suchas acetic acid,

propionic acid, etc., which arepresent in minorproportions and would beinsoluble in pentane, nevertheless they may be takenas approximateindicationsof the Oxy-acid concentration. These This is undesirable,however. for economic commex-cial operation. likewise the oxidation maybe continued for a substantial extent past the point of maximum yield,and by appropriately adjusting conditions in the subsequent purificationsteps a purified product suitable for compounding soluble oil may beobtained in relatively low yield.

` The decrease in yield on continuing the oxidation past asaponiflcation value of 110-120 is due to the increased formation ofOxy-acids which have been found to be highly detrimental in soluble oilmanufactured in accordance with this invention. These Oxy-acids aresoluble in the reaction mixture and so remain dissolved therein duringthe oxidation, but are insoluble in light petroleum hypentane-insolubleoxy-acids are viscous, oily products having a clear, deep red color, andshould not be confused with the oil-insoluble sludge-like productscaused by too high oxidation temperature as referred to above. Thetabulated data indicate that no more than about l0 per cent .Oxy-acidsare present at the degree of oxidation corresponding to maximum yield(110-120 saponication value) but that further oxidation causes rapidincrease in the proportion of these undesirable reaction products. Suchlarger proportions, although being undesirable, are permissible to anextent provided conditions in the subsequent fractional acidificationstep are so adjusted as to avoid acidification of the oxyacid soaps andthus allow these components to be substantially removed from thedesirable oxi- -dation products. When the oxidation is carried to adegree considerably beyond that contemplated by the present invention,a, point eventually is reached at which incipient separation of highlyoxygenated acidic products from the reaction mixture will occur. Thesehighly oxygenated, reaction mixtureinsoluble products are not the sametype products as the Oxy-acids referred to above but represent a higherdegree of oxidation. The point oi incipient separation, which will notbe reached at a saponication value even as high as 180, corresponds to amuch more severe oxidation than is embraced by the present invention.

All of the steps in the process following the 1 oxidation step may becarried out at a temperaafter saponication, somewhat lower temperaturesmay be employed in the purification steps if desired, although thisusually tends to lengthen the time required for mixing and settlingoperations.

In the saponification step following oxidation it is requisite forsuccessful production of high vquality soluble oil that completesaponification be effected. Since ester-like oxidation products are thelast to saponify, incomplete saponiflcation will result in substantialamounts of esters remaining in the saponified mixture; and although amajor proportion will be removed in the deoiling step as recycle stock,the n'al product will contain an appreciable concentration of esters. Ithas been found that these esters are highly deleterious to the solubleoil, in that they undergo delayed hydrolysis on prolonged standing ofthe soluble oil, that is, they slowly hydrolize to the correspondingacids and alcohols, and in so doing eventually cause the soluble oil tochange from slightly alkaline to acidic with a resultant considerabledepreciation in the emulsion stability characteristics. If, throughincomplete saponicaton here, esters are permitted to be present in theproduct from the' purication steps but this ester-containing product iscompletely saponified in the step which just pre'- cedes the finalcompounding step thereby destroying all esters, nevertheless the desiredsoluble oil quality will not be attained due to the presence in thesoluble oil of an appreciable at 80-90 C. until complete saponication isobtained. An excess lof alkali may be added but this is not necessaryand merely results in an increased consumption of both alkali and themineral acid required in the fractionalacidiilcay tionstep. It isdesirable for the mixture during agitation to have a water content ofabout -20 per cent; this ensures fluidity, and facilitates intimatemixing. If air blowing is used as a means of agitation, water may beadded from time to time to compensate for that lost through evaporation.

'I'he saponied mixture contains a large proportion of unsaponiablematerial comprising unoxidized oil. alcohols, aldehydes, ketones and.the like. It obviously is rdesirable that this unsaponiable material beseparately recovered in order to provide recycle stock which. asv hasbeen explained, has a beneficial effect-in the oxidation step, as wellas to decrease the consumption of fresh charge stock per unit volume ofsoluble oil produced, since the fresh charge stock due to the intensivepretreatment usually required represents a considerable fraction of thelc ost .of the process and any saving in this starting materialconsequently is of considerable advantage. 4In order to separate asubstantial proportion oi' the unsaponiable material it has been foundnecessary to dilute the saponified mixture with water, otherwisesubstantially no separation is obtained. The following tabulation servesto show the effect of degree of dilution on the proportion ofunsaponilable material recovered after settling the diluted mixture forone-half hour at r It is noted that no appreciable increase in recovingsoap layer contains unsaponiable material in amount equivalent to about10 per cent of the charge to the oxidation step. It has been found thatthis unsaponiable material later is bene-4 cial in that it improvescompatibility between the synthetic acids and hydrocarbon oil, im-Vproves compatibility between soaps of the acids and such oil, and4improves emulsibility of the soluble oil-product. If this 10 per centunsaponifiable lmaterial is removed from the soap layer, `for instanceby extraction witha low boiling naphtha, before further processing, thenal solubleoil product will lhave definitely poorer emulsion stabilitycharacteristics than otherwise.

In the fractional acidification' step it is of prime importance that theproper proportion of mineral acid be added. If too vsmall a proportionis used, a low yield of desirable product will result; on the. otherhand, if too large a proporition is used, the resulting product willcontainl acids having relatively strong acidic properties,

which is highly undesirable since the 'soaps of such acids tend to beoil-insoluble and cause gelation as well as poor emulsibility of thefinal soluble oil. The correct proportion of mineral acid to use dependsmainly on the amount of-oxyacids formed during oxidation, and also maydepend to an extent on the particular pressure employed in the oxidationstep, since the retention of the verylow boiling acidic products is4related to this factor. When the oxidation is effected under thepreferred pressure and is carried to a degree corresponding to asaponification value 'of 110-120, a .proportion of mineral acidequivalent to about per cent of the carboxyl groups should be used.Also, since there is little difference in the percentage of Oxy-acidsformed for lowerdeg'rees of oxidation, about the same -proportion ofmineral acid is required when the oxidation is stopped at saponiicationvalues below 11G-120. However, for higher saponification values,correspondingly smaller proportions of mineral acid are required due toincreased percentages of Oxy-acids.

It has been found that complete'removal of the undesirable componentsdoes not result when the fractionally acidied mixture is allowed toseparate into aqueousand oily layers and the aqueous layer is withdrawn.Instead the oily layer conof relatively strong acids, which must beremoved a vin order to yield a product suitable for making high qualitysoluble oil. Substantially complete `1 removal of these undesirableconstituents is ei'- fected in the water washing stepas described above.Although there is a tendency toward emulsion formation in this stepsince only a small -tion step has been used and that lubricating oil hasbeen added in amount equal to the desirablek synthetic acids. Thedifference between saponiiication and acid values indicates the presenceof some diicultly neutralizable constituents, believed to be lactones,the soaps of which readily are formed in the subsequent saponifyingstep. It should be understood that these lactones. al-

though they represent a higher degree of oxidation than simplecarboxylic acids, are not the same as the Oxy-acids referred to above,but, in contradistinction to said oxy-acids, are substantiallypentane-soluble and form soaps which appear to have a beneiicial ratherthan detrimental A effect on the quality of the nished soluble oil.

The last step in the process before finally com pounding the soluble oilcomprises saponication of the refined stock resulting from the abovedescribed purication procedure. This is accomplished by mixing therei-ined stock with a strong aqueous solution of an alkali metalhydroxide, preferably with 50 B. caustic soda, at 8090 C. and forsuicient time to effect substantiallycomplete saponliication. A smallexcess of alkali is used so that the finally compounded soluble oil willbe slightly alkaline, preferably so that it will have a free alkalinityequivalent to G01-0.10% NaOH. It has been found to be of primeimportance that this saponication be carried vout before 'the refined`stock is blended with other ingradients of the soluble oil; forotherwise, the compounded soluble oil on standing may exhibit gelation.No reason is apparent as to why the specific order of saponicationfollowed by blending is of such importance; nevertheless, it has beenfound effective as a means of avoiding this undesirable gelationtendency.

The final step of compounding the soluble oil comprises blending thesaponied stock, suitably at 80-90 C., with lubricating oil and vari- (2)Sulfonate concentration as indicated bythe organic S03 content.

(3) Mutual solvent content. (4) Water content. It has been found thatthe best grade soluble oil should conform tothe followingspecifications: Y

Equivalent carboxyl saponiiication value l18-20 Organic S03 content0.45%*minimuin Mutual solvent vcontent 0.5% minimum Water content2.5-2.75%

, asados? oil should be slightly alkaline, for instance containingG01-0.10% free NaOH.

When the soap content is equivalent to a carboxyl saponication value ofless than about 18. emulsibility` usually is not up to the desiredstandard for highest grade soluble oils; on the other hand, when itexceeds the concentration indicatedv by a carboxyl saponification valueof about 20,

there is an increasing tendency for the undiluted soluble oil blend toexhibit heterogeneity or incompatibility oi the soaps and hydrocarbonoil. A soap concentration within the range equivalent to lll-204carboxyl saponification value therefore is preferred, although somevariation of these limits is permissible when high quality is not re-lquired.

Sulfonates are added to the soluble oil for the purpose of impartingrust-inhibiting characteristics thereto. It has been found that when thesoluble oil is used as cutting oil in metal working operations thepresence of sulfonates in concentrations speciiled herein preventsrusting of the, metal under service conditions. Sulfonates derived frompetroleum lubricating oil fractions by treatment with strong sulfuricacid followed by neutralization with an alkali metal hydroxide aspracticed in white oil manufacture have particula;` utility for thepurpose. The'percentaee of or.t ganic S03 alfords a convenient means ofindicating the proper sulfonate concentration. In order to attain thedesired rust-preventive characteristcs the sulfonate content should beequivalent to not less thanabout 0.45% organic S03, for instance between0.45% and 0.60%, when sodium sulfonates resulting from 'white oilmanufacture are used. Larger proportions of sulfonates may be employed,although this usually effects little if any further improvement inquality of the soluble oil; however, since sodium sulfonates themselvesare good emulsifying agents, the use of such I larger proportions willpermit lower concentrations of the synthetic acid soaps than specifiedabove without loss of quality.

A minor proportion of a mutual solvent (i. e. a solvent for both oil andwater) is added to ensure compatibility of the blended constituents, toreduce viscosity of the blend and to aid emulsibility. Butyl Cellosolveis preferred as the mutual solvent, although various other solvents suchas iso` propyl alcohol and other alcohols and alcoholesters may be used.It is desirable to have at least 0.5% mutual solvent in the soluble oilblend but more than 1.0% is seldom if ever required.

The water content of the nal blend should lie within a rather narrowrange for best results. preferably within the range of 2.5-2.75%. al-

though a range of 22S-3.0% is permissible. Be-

low 2.25% there is a tendency for gelation to ocour, while above 3.0%there is danger of reaching a Vstate of incompatibility of soaps andoil. Usually the water content is adjusted before addition of the mutualsolvent in order to prevent loss of the latter.

While the addition'of minor amounts of sulfonates', a mutual solvent andwater are essential to the attainment, in the highest degree. of thequalities desirable in the finished soluble oil, it will be understoodthat their addition to such oils is known in the art and such additionis not included in the appended claims, which are confined to theprocess of producing the soluble oil to which said special ingredientsare added.

The viscosity of the lubricating oil used in compounding with theseother ingredients to produce In addition to these specifications thesoluble 75 a finished soluble ci; product is of relatively minorimportance. A lightflubricating oil, for instance one` having a.viscosity of 100 seconds S. U. at 100 F., is preferred in order that theviscosity of the product will not be excessive.

Soluble oils prepared in the above described manner are compatible withsoluble oils made from natural naphthenic acids and may be blendedtherewith in any proportion. In some cases this may result in a blend ofhigher quality in certain respects than either blend alone. Furthermore,refined synthetic acids obtained from the purifying procedure describedabove may be blended with natural naphthenic acids and the blend thencompounded with the other specified ingredients to produce solubleA oil,the only desirable alteration in the soluble oil formula then being aslight reduction in the optimum water content. i

Considerable latitude is permissible in the choice of equipment suitablefor practicing the present invention commercially. As previously stated,the process may be operated in a continuous manner, in which case theequipment .would be designed accordingly; however it is preferable tooperate batchwise since simple conventional types of commercialequipment then may be employed. Although the process comprises numeroussteps, only two major pieces of commercialequipment are needed in orderto carry out all of these in batch operation; specically, there isrequired an autoclave for the oxidation step and one conventional typeagitator for all the other steps including the final steps ofsaponifying the synthetic stock and compoundingthe soluble oil. Theautoclave should be constructed of material resistant to the corrosiveaction of the oxidation products and should be designed so as towithstand the desired pressure. It should be provided with an air inletline at the bottom and a vent gas line at the top, and with suitablevalves for regulating the gas flow and maintaining the desired pressure.It also should be provided with a means for intimately' mixing the airand the charge stock, aparticularly suitable means being a motor drivenimpeller or turbine-type stirrer. In addition, since the oxidationreaction is highly .exothermic, a cooling coil or other suitable meansshould be provided for absorbing the heat of reaction and maintainingthe temperature. at the desired level. Also some means for heating thecharge stock to the desired reaction temperature bottom type agitator,having suilicient heating coils for maintaining the desired temperatureand provided with means for effecting agitation such as an air supplyline for blowing, is suitable.

The following example will serve to show how the present invention maybe carried out in commercial practice: A

Twenty barrels of a 270 S, U. viscosity, white oil, obtained bytreatment of a Gulf Coastal distillate fraction with fuming sulfuricacid and composed 'of 1% aromatic rings, 59%' naphthene rings and 40%paraiilnic chains as determined by Watermann analysis, were charged to abarrel autoclave of the indicated design. Twenty-one barrels of theunsaponiable portion of oxidation product derived' from .a previousoperation were added to the autoclave and mixed with the fresh chargestock.A 'The mixture was effected by means of an impeller-type mixer. A

pressure oi' 50 pounds per square inch gauge wasl maintained within theautoclave, with airbeing supplied at the rate of about 520 cubic feetper minute (measured at atmospheric pressure) and vent 4gases beingwithdrawn at the approximate rate of 420 cubic feet per minute.Temperature was maintained at approximately 140 C. throughout theoxidation by means of cooling Water circulated through a coil.A Afterapproximately eight hours the oxidation was discontinued. The oxidizedmaterial comprised approxf imately 4 1 barrels having saponiiication andacid values of 114.5 and 54.3, respectively. 'I'his mate rial was pumpedfrom the autoclave into an opentop agitator of approximately 200 barrelscapacity and there allowed to cool to C. 4.2 barrels of 50 B.causticsoda solution and approximately the same amount of water wereadded, and the Amixture was agitated by blowing with air, the

for one-half hour. An upper layer comprising` 21 barrels of oil andwater-insoluble unsaponiii-` able oxidation products and a lower layercomprising 151.3' barrels of soap solution were obtained. The upperlayer was pumped oil' through a swing line and used as recycle stock ina subsequent oxidation. To the soap layer was added 21 barrels of,alight lubricating oil having a viscosity of 100 seconds S.`U. at 100 F.and 1.08 barrels of sulfuric acid calculated to be sufficient foracidifying 50 per cent of the soaps. The mixture was thoroughly agitatedand then permitted to stand for two hours at approximately 80 C.,whereby an upper layer comprising 37 barrels of oil-synthetic acidsmixture and a lower layer comprising 136 barrels of an aqueous solutionof soaps of relatively strong acids and sodium sulfate were obtained.The aqueous layer was drawn off and discarded. The. upper layer wasagitated with 37 barrels of water and then allowed to settle for twohours at about 80 C. The

v resulting aqueous layer again was drawn off andl discarded. The upperlayer contained a small amount of entrained water which was removedV byair blowing. Thirty-five barrels of refined 'stock having saponiilcatlonand acid values of 49.4 and 30.2', respectively, thereby was obtained.

The refined stock was saponli'led with 1.6 barkali. Saponication was'accomplished by blowing the mixture of rei-ined stock and alkali at 80C. for about one-half hour. To the saponined stock 47.2 barrels of lightlubricating oil similar to that described above, 5 barrels of crudepetroleum sulfonates (mixture oi' lubricating oil and sodium sulfonates)containing 7.4% organic S03, and 1.7 barrels of water were added,'andthe resulting mixture was blown with air until substantiallyhomogeneous. 0.5 barrel of butyl Cellosolve then was added and themixture again blown i'or a short time, whereupon a nnished soluble oilproduct meeting the following speciilcations was obtained:

Equivalent carboxyl saponication value-- 19 Organic SO; per cent-- 0.46Butyl Cellosolve do 0.5 Water do 2.6 Free NaOH do ,0.08

kThis product was found to conform to highest standards for cutting oilsin laboratory tests and under actual service conditions.

We claim:

l. The process of producing soluble oil from petroleum hydrocarbonstarting material having lubricating oil consistency and containingnaphthenic constituents in amount providing an average of at least onenaphthenic ring per molecule and aromatic constituents in amountinsuilicient substantially to inhibit oxidation, which comprisessubjecting said starting material to liquid phase partial oxidation bymeans of a free-oxygen containing gas at a. temperature within the rangeof 1Z0-165 C. and at a superatmospheric pressure not in excess of 175pounds per square inch, the conditions of temperature. and pressurebeing such as to elect a commercially practical rate of oxidation butsaid temperature being suillciently low to prevent the formation oisludge-like products, continuing the oxidation until the oxidizedmixture contains a substantial proportion of synthetic acids suitablefor soluble oil manufacture while avoiding the formation of more highlyoxidized acidic products in appreciably detrimental proportion, treatingthe oxidized mixture with an aqueous solution of alkali metal hydroxideunder such conditions as to effect complete saponification and yield anaqueous mixture comprising alkali metal soaps, unsaponiable oxidationproducts and unoxidized hydrocarbons, fractionally acidifying saidaqueous mixture with a mineral acid in amount sufcient to convert tofree acids a predominant -proportion of the soaps of relatively weakacids having utility in manufacture: of high quality soluble oil butinsufllcient to acidify a substantial proportion of the soaps ofrelatively strongr acids having characteristics detrimental to highquality soluble oils, separating resulting aqueous and oily phases,washing the oily phase with Water to remove water-soluble contaminantstherefrom and thereby yield a refined synthetic acid product the acidicconstituents of which include no substantial4 proportion of relativelystrong acids, saponifying said product with an alkali metal hydroxideand blending the .saponiiied product with petroleum oil to yield, as thedesired iinal product, a blend capable of forming stable oil-in-wateremulsions.

2. The process of producing soluble oilfrom petroleum hydrocarbonstarting material having lubricating oil consistency and containingnaphthenic constituents in amount providing an average of at least onenaphthenic ring per molecule and aromatic constituents in amountinsufflcient substantially to inhibit oxidation which com- Iprisesblending said starting material with the v recycle stock hereinafterspecified, subjecting the blend to liquid phase partial oxidation bymeans of a free-oxygen containing gas at a temperature within the rangeof l20-.-l65 C. and at a superatmospheric pressure not in excess of 175pounds per square' inch, the conditions of temperature and pressurebeing such as to effect a commercially practical rate of oxidation butsaid temperature being sufliciently low to prevent the formation ofsludge-like products. continuing the oxidation until the oxidizedmixture contains a substantial proportion of synthetic acids suitablefor soluble oil manufacture while avoiding the formation of more highlyoxidized acidic products in appreciably detrimental proportion, treatingthe oxidized mixture with an alkali metal hydroxide under suchconditions as to eiect complete saponiication, diluting the saponifledmixture with water, separating from the diluted mixture an oily phasecomprising unsaponiable material suitable for use as recycle stock in asubsequent oxidation, fractionally acidifying the remaining aqueouslayer with a mineral acidin amount sufficient to convert to free acids apredominant proportion of the soaps of relatively weak acids havingutility in manufacture of high quality soluble oil but in suiilcient toacidify a substantial proportion of the soaps of relatively strong acidshaving characteristics detrimental to high quality soluble oils,separating resultingy aqueous and oily phases, washing the oily phasewith water to remove water-soluble contaminants therefrom and therebyyield a rened synthetic acid product the acidic constituents of whichinclude no substantial proportion of relatively strong acids,saponifying said product with an alkali metal hydroxide and blending thesaponied product with petroleum oil to yield, as the desired finalproduct, a blend capable of forming stable oil-in-water emulsions.

3. The process as defined in claim 2 wherein lubricating oil is added tothe aqueous soap layer before subjecting said layer to fractionalacidification.

4. A soluble oil capable of forming stable oilin-Water emulsions whichcomprises a major proportion of lubricating oil, alkali metal soaps ofrelatively Weak synthetic acids having characteristics suitable formanufacture of high quality soluble oil in concentration equivalent to acarboxyl saponiiication value of 18-20 mgs. KOH per gram, alkali metalsulfonates in concentration atleast suicient to cause said soluble oilto have an organic S03 content of 0.45 per cent, at least 0:5 per centof an effective mutual solvent, 2.25-3.00 per cent Water and a smallpercentage of free alkali, said weak synthetic acids having beenderived,so as to exclude the presence therein of any substantialproportion of relatively strong synthetic acids detrimental to highquality soluble oil, from the reaction mixture obtained by liquid phasepartial oxidation of a petroleum lubricating oil fraction containing asubstantial proportion of naphthenic constituents under oxidizingconditions preventing the formation of sludge-like products.

5. The process of producing high quality soluble oil from petroleumlubricating oil containing an average of at least one naphthene ring per-molecule and aromatic constituents in amount insumcient substantiallyto inhibit oxidation. A

which comprises oxidizing said starting material in liquid phase bymeans of a free-oxygen containing gasat a temperature within the rangeof -l65-C. and at a superatmospheric pressure not in excess of 175pounds per square inch, discontinuing the oxidation when the reactionmixture has a saponiflcation value on the order of 110-120 milligramsKOH per gram, completely saponifying the reaction mixture with anaqueous solution of alkali metal hydroxide thereby to form an aqueousmixture comprising alkali metal soaps, unsaponiable oxidation productsand -unoxldized hydrocarbons, fractionally acidialkali metal hydroxideand blending the saponified product with petroleum oil to yield, as thedesired nal product, a blend capable of forming stable oil-inwateremulsions.

g 2,895,627 fying said aqueous mixture with -a mineral acid I 6. Theprocess according to claim wherein i the said starting material is anaphthenic base lubricating oil having la S. U. viscosity of about150-350 seconds at 100 F.

7. Theprocess of producing high quality soluble oil from petroleumlubricating oil containing an average of at least one naphthene ringvper molecule and aromatic constituents in amount insuicientsubstantially to inhibit oxidation,

which comprises oxidizing said starting material in liquid phase bymeans of a free-oxygen containing gas at a temperature within the rangeof 1Z0-165 C. and at a superatmospheric pressure not in excess of 175pounds per square inch, discontinuing the oxidation when the reactionmixture has a saponiflcation value on the order of 110-120 milligramsKOH per gram, completely saponifying the reaction mixture with anaqueous solution of alkali metal hydroxide, diluting the saponiledmixture with water, separating from the diluted mixture an oily phasecomprising unsaponiable material suitable for use as recycle stock in asubsequent oxidation, fractionally acidifying the remaining aqueouslayer with a mineral acid in amount required to acidify on theorder ofper cent of the alkali metal soaps -thereby liberating relatively weakacids having utility in manufacture of high quality soluble oil,separating resulting aqueous and oily phases, washing the oily phasewith Water to remove water-soluble contaminants therefrom and yield arened synthetic acid product the acidic constituents of which include nosubstantial proportion of relatively-strong acids detrimental to highquality' soluble oil, saponifying said product with an alkali metalhydroxide and blending the saponied product with petroleum oil to yield,as the desired nal product, a blend capable of forming stableoil-in-water emulsions..

8. The process according to claim 7. wherein the said starting materialis a naphthenic base lubricating oil having a S. U. viscosity of 150-350seconds at F. l v

9. A soluble oil capable of forming stable oilin-water emulsions whichcomprises a major proportion of lubricating -oil and a minor proportionof alkali metal soaps of relatively weak synthetic acids possessing thecharacteristics ofthe acid fraction obtained by oxidizing a naphthenicbase lubricating oil of about 270 S. U.' viscosity at 100 F. in liquidphase by means ofa free-oxygen containing gas at a temperature withinthe range of 12o-165 C. and a superatmospheric pressure below 175 poundsper square inch, discontinuing the oxidation when the reaction mixturehas a saponification value of -120 milligrains KOH per gram, completelysaponifying the reaction mixture with an alkali metal hydroxide,fractionally acidifying about 50 per cent oi' the soaps in the saponiedmixture to obtain a relatively' weak acid 'fraction and washing' saidfraction with water. t Y HERBERT L. JOHNSON.

JOHN HAROLD PERRINE.

